In vitro and in vivo data support the carcinogenic potential of cadmium (Cd) and its role in breast cancer development. Increased human exposure to Cd has raised concern about the association between this heavy metal and risk of breast cancer. However, only one epidemiologic study has been published that addresses this emerging environmental exposure. This project aims to evaluate the association between Cd exposure and breast cancer risk using data collected from an on-going population-based case-control study of breast cancer (R01 CA47147) supplemented with proposed urine sample analysis. The main hypothesis of interest is that higher body burden levels of Cd as measured in urine are associated with an increased risk of breast cancer. Secondary hypotheses are: 1) self-reported personal smoking history and exposure to tobacco smoke are related with measured Cd and 2) age, geographic location, parity, menopausal status, occupation, consumption of supplemental minerals and food with potentially high Cd levels are related with Cd body burden. To accomplish these aims, 250 newly diagnosed breast cancer cases (identified by Wisconsin's statewide tumor registry) and 250 population controls enrolled in the parent study will be asked about their exposure to factors hypothesized to be associated with Cd body burden. This information will supplement existing questions regarding established risk factors for breast cancer. Women will also be asked to collect a urine sample at home and to mail it to the study office. Urine samples, the most relevant practical biological indicator of long-term Cd exposure, will be expertly analyzed by the Wisconsin State Lab of Hygiene to measure body burden of Cd. interview data will be merged with urine Cd level data to address the specific aims. The study team brings together expertise in breast cancer and environmental epidemiology, laboratory science, and biostatistics to efficiently address the role of cadmium in the etiology of breast cancer.